A variety of parallel optical communications modules exist for simultaneously transmitting and/or receiving multiple optical data signals over multiple respective optical data channels. Parallel optical transmitters have multiple optical transmit channels for transmitting multiple respective optical data signals simultaneously over multiple respective optical waveguides (e.g., optical fibers). Parallel optical receivers have multiple optical receive channels for receiving multiple respective optical data signals simultaneously over multiple respective optical waveguides. Parallel optical transceivers have multiple optical transmit and receive channels for transmitting and receiving multiple respective optical transmit and receive data signals simultaneously over multiple respective transmit and receive optical waveguides.
For each of these different types of parallel optical communications modules, a variety of designs and configurations exist. A typical layout for a parallel optical communications module includes a circuit board, such as a printed circuit board (PCB), a ball grid array (BGA), or the like, on which various electrical components and optoelectronic components (i.e., laser diodes and/or photodiodes) are mounted. In the case of a parallel optical transmitter, laser diodes and one or more laser diode driver integrated circuits (ICs) are mounted on the circuit board. The circuit board has electrical conductors running through it (i.e., electrical traces and vias) and electrical contact pads on it. The electrical contact pads of the laser diode driver IC(s) are electrically connected to the electrical conductors of the circuit board. One or more other electrical components, such as a controller IC, for example, are typically also mounted on and electrically connected to the circuit board.
Similar configurations are used for parallel optical receivers, except that the circuit board of the parallel optical receiver has a plurality of photodiodes instead of laser diodes mounted on it and a receiver IC instead of a laser diode driver IC mounted on it. The receiver IC typically includes amplification circuitry and sometimes includes clock and data recovery (CDR) circuitry for recovering the clock and the data bits. Parallel optical transceivers typically have laser diodes, photodiodes, one or more laser diode driver ICs, and a receiver IC mounted on it, although one or more of these devices may be integrated into the same IC to reduce part count and to provide other benefits.
FIG. 1 illustrates a perspective view of a parallel optical communications module 2 known as a CXP module. The CXP module 2 is a pluggable module that typically has twelve transmit channels and twelve receive channels. The CXP module 2 is relatively compact in size and is configured to be plugged into a receptacle disposed in a front panel of a 1U box (not shown). Typically, multiple CXP modules of the type shown in FIG. 1 are plugged into respective side-by-side receptacles of a 1U box. The heat that is generated by the electrical and optoelectronic components, such as the ICs and laser diodes, for example, is transferred through the metal module housing 2a into an external heat dissipation device 3, which dissipates the heat.
The size of a heat dissipation device is directly proportional to the heat rise and its heat load. It can be seen from FIG. 1 that the size of the external heat dissipation device 3 is large compared to the size of the CXP module 2. For this reason, the heat dissipation device 3 consumes a relatively large amount of space inside of the 1U box. Specifications for the CXP module 2 set an upper limit on the temperature of the module housing 2a at 80° Celsius (C) and an upper limit on the temperature of the air inside of the 1U box at 70° C. The heat dissipation device 3 is designed to dissipate heat in a manner that allows these limits to be met.
The laser diodes of the CXP module 2 are very sensitive to increases in temperature. Generally, in order to increase the speed of the laser diodes without sacrificing performance, the operating temperature of the laser diodes needs to be lowered. One solution that would allow for a significant increase in the data rate of the laser diodes of the module 2 without degrading their performance would be to significantly increase the size of the heat dissipation device 3. However, because the heat dissipation device 3 is already relatively large, further increasing its size is not a desirable solution for a variety of reasons. For example, increasing the size of the heat dissipation device 3 could decrease module mounting density and increase costs.
Accordingly, a need exists for methods and systems that provide improved heat dissipation solutions and that are efficient in terms of space utilization.